Columbia CNA Agar Medium is used with blood in isolating Gram-positive cocci. Eliner et al. added Colistin Sulfate and Nalidixic Acid to Columbia Agar to suppress the growth of Gram-negative bacteria. The addition of 5-10% sheep red blood cells to the base demonstrates hemolytic patterns of Staphylococci and Streptococci. Peptone and Peptic Digest of Animal Tissue provide nitrogenous sources, vitamins, and minerals. Corn Starch is the source of carbohydrates. Sodium Chloride maintains the osmotic equilibrium and Agar is the gelifying agent.